Method of food decontamination by treatment with ozone

ABSTRACT

The present invention provides a system for the decontamination of agricultural products by reacting the toxins and microorganisms, contaminating the product, with ozone. The ozone is generated on site and upon demand, thus eliminating ozone waste associated with long periods of ozone storage. The systems of the invention provide efficient, safe, and environmentally friendly use of ozone for product decontamination by optimizing the delivery of ozone to the contaminated product, monitoring and controlling the pressure in the treatment systems, monitoring and controlling the heat generated during the treatment of contaminated product with ozone, and controlling ozone release into the atmosphere.

This application is a continuation of U.S. patent application Ser. No.09/018,614 filed on Feb. 4, 1998.

This invention was made with government support under grant95-33610-1429 awarded by the United States Department of Agriculture(USDA). The government has certain rights in this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to techniques and devices for thedecontamination and preservation of food products exposed to spoilingmicroorganisms and/or toxins. The invention more particularly relates tothe use of ozone in the detoxification of agricultural productscontaminated with mycotoxins.

2. Background of the Related Art

Mycotoxins are naturally occurring chemical compounds produced bycertain species of fungi (e.g. Aspergillus sp., Fusarium sp.,Penicillium sp.) which commonly grow on and infest plant materials suchas grains, oilseeds and grasses. They are most often produced in thefield under conditions of environmental stress on the plant (e.g. heat,insects, and drought). Aflatoxins are prevalent mycotoxins that presentremarkable toxicity and hepatocarcinogenicity, that is, aflatoxins cancause diverse toxic effects on virtually all organs, eventually leadingto the development of cancerous tumors capable of spreading throughoutthe entire body. There are four major aflatoxins (AfB₁, AfB₂, AfG₁ andAfG₂) that contaminate crops, with aflatoxins AfB₁ and AfG₁ havinggreater toxic potential than aflatoxins AfB₂ and AfG₂. The InternationalAgency for Research on Cancer has particularly noted the major forms,AfB₁ and AfG₁, as potent carcinogens, linked primarily to cancer of theliver. Thus, the amount of aflatoxin allowed in human and animal food isregulated by state and federal agencies.

Fumonisin B₁ is a mycotoxin that occurs almost exclusively on corn andcan cause toxic effects in horses and swine. fumonisin B₁ has beenlinked to esophageal cancer in humans and has been shown to be a cancerinitiator and promoter in rodents. Tricothecenes (e.g. T-2 toxin,deoxynivalenol or ‘vomitoxin’), ergot, zearalenone, cyclopiazonic acid,patulin, ochratoxin A, and secalonic acid D are mycotoxins that cannegatively impact human and animal health due to their diverse toxiceffects. The toxic effects caused by these mycotoxins may be classifiedas acute or chronic, depending on the level and duration of mycotoxinexposure and species sensitivity.

Virtually all animals in the food chain can be affected by exposure tocontaminated food and feed, including humans, who can be exposeddirectly to toxins through grain handling and consumption or indirectlythrough consumption of an unmetabolized parent compound or toxicmetabolic products in contaminated meat or livestock products (e.g. milkand cheese.) As a result, mycotoxin contamination of agriculturalcommodities, such as corn, wheat, rye, rice, barley, oats, peanuts,pecans, soybeans, cottonseed, apples, grapes, alfalfa, clover, sorghum,and fescue grass forages, can result in severe economic loss at alllevels of food production (e.g. cost of pre-harvest prevention,post-harvest treatment, down-grading, loss of contaminated grain,decreased animal productivity and increased loss of livestock, healthcare costs, etc.) Thus, a need has long been recognized for techniques,methods, and devices that would help reduce the levels of multiplemycotoxins in feeds for livestock and food for human consumption.

In U.S. Pat. No. 4,421,774, Vidal et al. disclose a method forpreventing sprouting and mold and fungi proliferation in stored grainhaving moisture content in excess of 15%. The disclosed energy intensivemethods of stored grain preservation include heating the grain andreducing the moisture content to below 15%. Treatment with 1% propionicacid has also been shown to prevent microbial growth, however, the colortexture and taste of the grain may be affected and thus grain treated bythe methods disclosed by Vidal et al. can only be used in the treatmentof animal feed.

Vidal et al. also disclose a method wherein sulfur dioxide gas isbubbled through a propionic acid solution. The gas is used to transportthe vapor pressure qualities of the acid to the grain mass. After agiven period of time, the grain is perfused with ammonia gas. Theprocess is designed to prevent the formation of A. flavus (a fungus)during storage, thus preventing the formation of mycotoxins. However,the process is not capable of removing aflatoxins that are present onthe grains before being placed in storage.

In U.S. Pat. No. 4,035,518, Carmona et al. disclose a methodparticularly adapted for the treatment of nuts contaminated withaflatoxins. The nuts are placed in a 0.10% sodium hydroxide solution ata temperature of 212° F. for 10 minutes. The nuts are then removed andwashed in water until a neutral pH is attained. During this washing, theskins of the nuts are loosened by the sodium hydroxide and washed awayallowing for color differentiation between the lightly coloreduncontaminated peanuts and the deep dark contaminated peanuts. The colordifferences allow the contaminated and uncontaminated nuts to be sortedelectronically. However, this process does not allow detoxification ofthe food contaminated with aflatoxins.

In U.S. Pat. No. 4,795,651, Henderson et al. use a flotation method toseparate the contaminated grains or kernels. The authors describemethods that can be used to reduce the amount of aflatoxin contaminatedmaterial from feeds by physically removing them. The contaminated seedsrise to the top in a flotation medium while the uncontaminated seedssink to the bottom. These processes present at least two drawbacks: 1)the high cost of removing and disposing of the contaminated materials inaccordance with environmental guidelines, and 2) the difficulty ofachieving complete removal of the contaminated kernels, seeds, etc.without wasting significant portions of the uncontaminated product.

Another method of removing mycotoxins is by altering them chemically bystructural degradation following chemical treatment, or by physicalabsorption onto a reactive substrate. In U.S. Pat. No. 5,230,160, Grosset al. use microwaves and an applied vacuum to extract oil and moisturefrom seeds and nuts. The disclosed methods are designed as conventionalcontinuous-type processes for the treatment of contaminated nuts. Thecontaminated food passes through a vacuum chamber where the microwavesare applied. The methods are based on the assumption that oil and watervapor fractions absorb the aflatoxins thus removing them from the foodmatrix. The water/oil/aflatoxin vapor is then condensed and removed. Theaflatoxins can then be decontaminated before the mixture is discharged.One caveat presented by this technique is the need for extraordinarycaution not to overheat the foods which necessitates that the microwavepower be decreased incrementally along the chamber. Also, the heatingprocess does not successfully destroy the aflatoxins (aflatoxins arerelatively heat stable) nor does the treatment with microwaves.

In U.S. Pat. No. 5,165,946, Taylor et al. describe an inorganic animalfood additive that chemically binds to and inactivates aflatoxins bycombination in the gastrointestinal tract of the animal. Aphyllosilicate clay is produced in pellet form and fed to livestockalong with the mycotoxin contaminated meal. The aflatoxin binds to theclay during digestion and is excreted in the feces of the animal.

In U.S. Pat. No. 5,498,431, Lindner describes a method of detoxifyingmycotoxins by an energy intensive process. Timed or untimed pulses ofultrasonic radiation are passed through an aqueous solution containing asuspension of grains or ground meal. In some cases, addition ofalcohols, dilute acids and ammonia water to the aqueous suspension hasbeen found to be somewhat beneficial. The radicals that are produced bythe microcavition reaction attack the epoxide region of the varioustrichothecene mycotoxin molecules.

Treatment of grain with ammonia gas or ammonium hydroxide liquid hasbeen found to reduce aflatoxin levels in corn, peanut meal, wholecottonseed and cottonseed products. Two procedures have been used in theammoniation process: (1) High Temperature/High Pressure treatment,(HP/HT), and (2) Atmospheric Pressure/Ambient Temperature treatment,(AP/AT). HP/HT procedures involve the treatment of the contaminatedproduct with anhydrous ammonia and water in a sealed vessel. Thequantity of ammonia used in the treatment may vary between 0.5 and 2.0%while the moisture content is generally maintained between 12 and 16%.This treatment is maintained for up to one (1) hour at temperaturesbetween 80 and 120° C. and pressures around 50 psi. In the AP/ATprocess, a 13% ammonium hydroxide solution is sprayed onto thecontaminated product as it is being packaged into a plastic silage bag.The bag is then sealed and held at ambient temperatures for between 14and 42 days. The bag is generally probed and tested periodically foraflatoxin levels. Other methods of introducing ammonia to thecontaminated products include using monomethylamine and lime in theHP/HT process or liberating ammonia using urea.

Ozone (O₃) gas has been used for the sterilization and preservation offood and has recently been granted GRAS (Generally Recognized As Safe)status by the Food and Drug Administration.

Ozone is a highly reactive compound having a half life in air of only 24hours. Ozone tends to react spontaneously and decompose according to thefollowing reaction:

2O₃→3O₂

Ozone's high reactivity introduces numerous problems. For example, ozonedecomposition is easily accelerated by water, nearly all types oforganic chemicals, and many types of inorganic chemicals. Ozone is alsoa surface active material, i.e. ozone decomposition is accelerated whenozone comes in contact with a surface, especially if the surface isorganic in nature. Furthermore, ozone decomposition is accelerated athigher temperatures and pressures, by turbulence, ultrasound andultraviolet light. Thus, unlike most conventional gases, ozone is notsuitable for storage for more than a short period of time.

Where an ozone bearing gas is introduced into stored materials such ascereals, fruits, grasses, nuts and grains or other agriculturalproducts, the ozone bearing gas may pass through the space between thegrains of the material and displace air from the space around thematerial. Because of the generally organic nature of the storedmaterials and the high surface contact area of the grains, ozone mayrapidly react and decompose into oxygen as it is being passed throughthis type of matrix. Therefore, it is generally difficult to maintainsteady ozone concentrations in the interstices of the material to ensureadequate and uniform treatment of all the material in a storagecontainer.

Ozone's high reactivity poses special problems when attempting tointroduce and pass ozone though a porous organic medium such asagriculturally derived substances. In particular, special considerationmust be given to controlling the dosing rate and achieving adequatelyhigh ozone concentrations uniformly throughout the entire stock of thestored material.

Uniform distribution of the ozone gas through the treated material maybe complicated by multiple factors. For example, ozone reactivity may beso vigorous that when an ozone bearing gas is introduced into spacesaround a material like grain or cereal, ozone may react immediately inthe vicinity of the gas entry port resulting in excessive heating andaccelerated ozone decomposition into oxygen in the immediate vicinity ofthe entry port. Furthermore, the ozone entry port may be overdosed withozone, while grains located away from the entry port may have limitedexposure to the ozone bearing gas. Furthermore, excess heating, which ismore likely to occur at or near the entry port, may present significanthazard such as explosion of the container and/or fire.

Another important consideration in designing systems for detoxificationby ozone treatment relates to the high cost of ozone generation.Decontamination by ozone treatment may only be cost effective if ozonewaste is minimized.

In U.S. Pat. No. 3,341,280, Eolkin describes a method of using ozone andother gaseous compounds as a sterilizing gas for batch treatments offood. The chamber containing the food is evacuated, filled withsterilizing gas, and after a given period of time, the system isevacuated again to remove the sterilizing gas. However these systemspresent two major caveats: 1) heavy duty gauge material is alwaysrequired in order to support the changes in pressure within thecontainer and 2) almost unavoidable loss of the treatment gas to theatmosphere when the system is vented.

In U.S. Pat. No. 3,592,641, Rayner et al. describe a method ofdetoxifying aflatoxins in oilseed meals using ozone gas. Distilled wateris added to ground meal to form a slurry with 22% to 30% water content.The mixture is then stirred and heated to a temperature between 75° and100° C. and gassed with 25 mg/min O₃ for 60 to 120 min. The ozonatedslurry is spread in a thin layer and air dried for 48 hours. While thetechnique allowed some decrease in aflatoxin contamination, itseffective implementation in enhancing the nutritional and toxicologicalqualities of the ozonated meal is drastically limited by the necessityto heat the mixture, which dramatically increases the rate ofdecomposition of ozone into molecular oxygen prior to ozone's reactionwith the aflatoxin molecule.

In U.S. Pat. No. 4,549,477, McCabe describes the use of ozone in acontinuous treatment ozone based process for the preservation of foodproducts. The food products are conveyed along an elongated housingstructure filled with ozone on a series of conveyor units. Ozone gas isdistributed at spaced locations along the conveyor belt so that ozonemay continually displace air or oxygen present in the chamber. Becauseozone is denser than both air and oxygen it acts as a blanket withlimited diffusion away from the food. The disclosed system suffersseveral limitations including the need for the storage of largequantities of ozone, as well the potential for ozone waste and releaseinto the atmosphere.

In U.S. Pat. No. 5,011,699, Mitsuda et al. disclose a method whereinozone gas is mixed with an inert gas such as carbon dioxide or nitrogento act as food sterilizer. The carbon dioxide gas may help the ozonepenetrate inside the food stuff being treated, and nitrogen gas may helpprevent the food stuff from changing color and from emitting offensiveodors associated with excessive oxidation. The disclosed technique,however, suffers from the same limitations as the ozone treatmentsystems discussed above, and does not provide for controlled supply andrelease of the ozone.

In U.S. Pat. No. 5,403,602, Endico uses ozonated water to act as anoxidizing agent in the treatment of food with ozone. An oxygen sensor isused to monitor the increase in oxygen gas resulting from thedecomposition of the ozone.

Thus, there is a need for ozone treatment systems, methods or devicesthat would partially or totally eliminate the need for storing ozoneprior to its use in treating contaminated materials. It would also bedesirable to provide improved systems of the introducing anddistributing ozone through the contaminated material so that thecontaminated material is uniformly exposed to the ozone. Furthermore, itwould be desirable if the system prevented overheating and pressurebuildup, made optimum use of ozone, and reduced or eliminated ozonewaste and transfer to the environment. More particularly, it would bedesirable to have a system that would provide better ozone treatment ofdry contaminated material.

SUMMARY OF THE INVENTION

The present invention provides a method for treating agriculturalproducts with ozone gas comprising: (a) placing the agricultural productin a treatment chamber; (b) generating ozone in the vicinity of thechamber; (c) supplying ozone to the product through an ozone deliverysystem in communication with the chamber having ozone delivery portspaired to ozone exit ports in the chamber, the pairing of the zonedelivery ports and the ozone exit ports creating a plurality of ozoneflow paths through the product; and (d) contacting the agriculturalproduct with the ozone. The contacting of the agricultural product withthe ozone preferably comprises reacting the ozone with the toxins and/ormicroorganisms in the agricultural product. The (c) and (d) steps of themethod may be conducted simultaneously or sequentially.

The method encompasses ozone treatment of agricultural productcomprising one or more toxins from the group consisting of aflatoxins,fumonisin B₁, ergot, zearalenone, cyclopiazonic acid, patulin,tricothecenes, ochratoxin A, and secalonic acid D.

The method may further comprise monitoring the temperature in thechamber and suspending ozone supply to the chamber when the temperaturereaches a given value. The method may also comprise monitoring andcontrolling the concentration of ozone in the chamber and destroying theozone exiting the treatment chamber.

The method of the invention encompasses controlling ozone delivery toparticular sections of the chamber by selective closing of one or moresets of paired ozone entry and exit ports. Pressure sensors may beplaced in the chamber near ozone exit ports to monitor and control thepressure inside the chamber. In particular, a selected set of pairedozone entry and exit ports may be opened or closed to control thepressure in the chamber. The chamber may also be communicated with oneor more temperature sensors placed near the ozone entry ports, and ozonesupply to the chamber through an ozone entry port may be suspended whenthe temperature near the entry port is higher than a given value.Further, The chamber may be communicated with one or more ozone sensorsplaced in the chamber near ozone exit ports and paired ozone entry andexit ports may be opened or closed to control the ozone concentration inthe chamber.

The ozone used in the methods of the invention may be generated by acorona discharge process or by an electrochemical process. The ozone maybe humidified before it is supplied to the chamber with or withoutmixing with a compressed inert gas.

The invention also encompasses supplying the ozone to the chamberthrough an ozone delivery system comprising a hollow tube withperforated holes in communication with an ozone generator. The hollowtube may be rotated to better distribute the ozone through theagricultural product in the chamber. The tube may also comprise wingsextending from the surface of the tube and facing upwards towards thetop of the chamber; the wings allowing lifting the agricultural productwhen the tube is rotated. The ozone may also be supplied bycommunicating the chamber with an ozone delivery system comprising amanifold in communication with an ozone generator and ozone entry portsin the chamber. Supplying the ozone to the chamber may also beaccomplished by communicating the chamber with an ozone delivery systemcomprising a blower in communication with an ozone generator and thechamber.

The agricultural product treated by the methods of the invention may beplaced in one or more chambers in communication with a common ozonesource.

The invention also encompasses an apparatus for the supply of ozone gasto a matrix of product comprising: an ozone generator; a treatmentchamber having a plurality of gas exit ports; an ozone delivery systemin communication with the ozone generator having a plurality of gasentry ports paired with the gas exit ports in the chamber; a pluralityof pressure sensors in communication with the treatment chamberpositioned near the gas exit ports; and a plurality of temperaturesensors in communication with the treatment chamber positioned near thegas entry ports.

The ozone delivery system of the invention may comprise a manifold incommunication with the ozone generator and the plurality of gas entryports; a blower in communication with the ozone generator and thechamber; and/or a hollow tube extending along the central axis of thechamber, in communication with the ozone generator and having ozoneentry ports in communication with the chamber. When the ozone deliverysystem comprises a tube, the apparatus may also comprise a rotatingsystem in communication with the tube. The tube may further comprisewings extending from the external surface of the tube in an angleddirection towards the top of the chamber.

Finally, the apparatus of the invention may comprise one or moretreatment chambers; each chamber having an ozone delivery system incommunication with the ozone generator.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the features and advantages of the present invention can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the embodimentsthereof which are illustrated in the appended drawings. It is to benoted, however, that the appended drawings illustrate only typicalembodiments of this invention and are therefore not to be consideredlimiting of its scope, for the invention may admit to other equallyeffective embodiments.

FIG. 1 is a schematic diagram of an ozone delivery and treatment systemof the present invention.

FIG. 2 is a schematic diagram of an ozone delivery system that can beused in conjunction with the ozone treatment system of FIG. 1.

FIG. 3 is a schematic diagram of a multiple-chamber ozone treatmentsystem of the invention.

FIG. 4 is a schematic diagram of an ozone treatment system with arotating ozone delivery mechanism.

FIG. 5 is a schematic diagram of an ozone delivery system with arotating mechanism and a set wings.

FIG. 6 is a schematic diagram of an ozone treatment system with ablower.

FIG. 7 is a graph illustrating the decrease in aflatoxin concentrationin 1 Kg of contaminated corn as a function of exposure time to acontinuous stream of ozone gas.

FIGS. 8(a-b) are graphs illustrating the amount of ozone supplied to thetreatment chamber during the first and fourth filling phases,respectively, in a series of successive treatment cycles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a system for the decontamination ofagricultural product by use of ozone in the scavenging of microorganismsinfecting the product and/or the oxidation of toxins present in theproduct. The ozone is preferably generated on site and upon demand, thuseliminating ozone waste associated with long periods of ozone storage.The systems provide more efficiency, safety, and environmentalfriendliness in the use of ozone for product decontamination byoptimizing the delivery of ozone to the contaminated product, monitoringthe pressure in the treatment systems, monitoring the heat generatedduring the treatment of contaminated product with ozone, and controllingozone release into the atmosphere.

While the detailed description of the invention may focus on the ozonetreatment of agricultural product contaminated with mycotoxins, andparticularly aflatoxins, the ozone treatment provided by the inventionis likewise effective in chemically inactivating a variety of toxins andscavenging a variety of microorganisms that may infect the agriculturalproduct. Examples of toxins that may be effectively eliminated by themethods of the invention comprise but are not limited to aflatoxins,fumonisin B₁, ergot, zearalenone, cyclopiazonic acid, patulin,tricothecenes, ochratoxin A, and secalonic acid D. Thus, all ozonetreatments of agricultural products using the methods and apparatus ofthe invention are encompassed by the invention and are considered withinthe scope of the present specification.

The invention provides an ozone containing gas for the treatment ofagricultural products, such as whole grains, seeds, nuts, spices,fruits, and grasses. The ozone provided by the invention may begenerated on-site by a device based on currently available technologiesor their equivalents. The techniques and devices of the invention may beadaptable for use with any advanced ozone generating system. On acommercial basis, ozone is currently produced by the silent electricdischarge process, otherwise known as corona discharge, wherein air oroxygen is passed through an intense, high frequency alternating currentelectric field. The corona discharge process forms ozone through thefollowing reaction:

³/₂O₂O₃ΔH°₂₉₈=34.1 kcal

Yields in an air fed corona discharge process are generally in thevicinity of 2 wt % ozone, i.e., the exit gas may be about 2% O₃ byweight. If the corona is provided with pure oxygen, the yield in ozonemay jump to 6 wt %. Such O₃ concentrations, while quite poor in anabsolute sense, are still sufficiently high to furnish usable quantitiesof O₃ for the indicated commercial purposes. Another disadvantage of thecorona process is the production of harmful NO_(x) otherwise known asnitrogen oxides. Other than the aforementioned electric dischargeprocess, there is no other commercially exploited process for producinglarge quantities of O₃.

However, O₃ may also be produced through an electrolytic process byimpressing an electric current (normally D.C.) across electrodesimmersed in an electrolyte, i.e., electrically conducting fluid or solidpolymer electrolyte. The electrolyte includes water, which, in theprocess dissociates into its respective elemental species, O₂ and H₂.Under the proper conditions, the oxygen is also evolved as the O₃species. The evolution of O₃ may be represented as:

3H₂OO₃+3H₂ΔH°₂₉₈=207.5 kcal

It will be noted that the ΔH° in the electrolytic process is many timesgreater than that for the electric discharge process. Thus, theelectrolytic process appears to be at about a six-fold disadvantage.Other methods and techniques for on-site production of ozone aredescribed in U.S. Pat. No. 5,460,705, incorporated herein by referencein its entirety.

The invention also provides means of delivering ozone gas or an ozonecontaining gas under controlled humidity, flow rate and ozoneconcentration to a contaminated product, or product to be preserved. Theozone containing gas may be produced with humidity as part of theproduction process, or the ozone may be humidified before delivery to atreatment chamber. The treatment chamber may the same or a differentvessel as that used for long term storage of the product to be treatedor preserved. Contaminated product may then be contacted with the ozonecontaining gas.

Ozone delivery may be controlled by placing one or several temperatureprobes at various locations within the treatment chamber. When a certaintemperature is reached, a temperature probe may send a signal to shutoff the delivery of ozone containing gas to the treatment chamber or aregion within the treatment chamber.

Further, the invention provides for better control of localizedoverheating through even distribution of the ozone gas throughout thetreatment chamber. The invention encompasses several techniques toevenly distribute the ozone, including (1) special ozone contactors tosupply the ozone to the contaminated product; or (2) a fan placed in thetreatment chamber to create a pressure gradient and distribute ozone orozone containing gas throughout the treatment chamber. Even distributionof the ozone bearing gas may also be achieved by placing multiple gasentry and exit ports at various locations on and within the storageunit, thus establishing different gas flow paths. The invention providesfor ozone release control by placing ozone detectors at strategicpositions around the treatment chamber. In order to closely monitorozone delivery and release, ozone detectors may be placed within thetreatment chamber, at gas entry and/or exit ports.

The invention allows for safer ozone treatment by providing one or moreozone destruction units that may be placed in the treatment chamber atone or more gas exit ports. Ozone destruction units may destroy anyozone that is being evacuated to the atmosphere. The invention alsoprovides pressure sensors that may be placed within the treatmentchamber to prevent pressure build-up by controlling the supply of ozoneto the treatment chamber, thus reducing the risk of damage to thetreated product and/or the treatment equipment.

The invention also provides for control of the degree to whichcontaminated product is treated so that over-treatment may be avoided.For example, over-treating the material may be avoided by analyzingsamples extracted from the treatment chamber at regular intervals. Onemethod provided by the invention for safe sampling comprises pumping airinto the treatment chamber and forcing ozone through the exit portswhere it is destroyed by the ozone destruction units. Ozone detectorsmay then signal the point at which the ozone has been destroyed,allowing for safe removal of samples that may be analyzed.

One aspect of the invention provides an apparatus for decontaminatingproducts contaminated with mycotoxins or preventing mycotoxincontamination of products stored for long periods of time underconditions that would otherwise promote contamination. The apparatus maycomprise a treatment chamber, preferably made of or having a coating ofozone resistant material, in which the product may be loaded byconventional methods such as the use of an auger or a conveyor. Thetreatment/storage chamber allows the product to surround an ozonedelivery system comprised of one or more ozone resistant hollow tubes,allowing distribution of the ozone containing gas throughout the matrixof product being formed. The hollow tubes may comprise perforationsalong their length for ozone supply to the matrix. The tubes may beplaced in a variety of positions and locations within the treatmentchamber, preferably in a vertical position down the center of thetreatment chamber which may be of any shape.

The ozone gas may be supplied by an on-site ozone generator, such as acorona discharge in treatments requiring only low concentrations ofozone or an electrochemical ozone generator in treatments requiring highconcentrations and/or pressurized ozone gas. Prior to use in thetreatment chamber, the ozone containing gas may be passed through ahumidifier where it may take up moisture. Moisture content of the ozonegas used for treating mycotoxins may range from 0% to 100%, depending onthe type of treatment. In treatments for aflatoxin decontamination ithas been found that ozone with a humidity content in excess of 80% isgenerally effective and could produce complete decontamination. Oncehumidified, if at all, the ozone containing gas is then passed into thedistribution system where it may be distributed to different locationsin the product matrix and displace the air that normally resides in theinterstitial space within the matrix formed by the product.

In order to prevent over-pressurizing the treatment/storage chamber withozone, one aspect of the invention provides gas vents placed on the sideof the chamber and opened either periodically or when pressure sensorspositioned inside the chamber indicate a pressure inside the chamberthat is higher than a given value. When the pressure sensors detect ahigh pressure inside the chamber, it is preferred to stop the supply ofozone to the treatment chamber.

Another aspect of the invention provides control of the exothermicreaction between ozone and the stored product to prevent overheating.Because ozone may react as soon as it contacts the product, hot spotsmay be created within the matrix, particularly at ozone delivery ports.To prevent excess heating, one or more temperature sensors may bepositioned within the treatment chamber. When the temperature reaches agiven setpoint, the supply of ozone may be stopped, and/or ozone may bedispersed through the matrix by creating in the chamber, for adetermined period of time, a succession of positive and negativepressures. The intermittence of negative and positive pressure withinthe chamber may not only disperse the ozone but also help regulate thetemperature. The temperature sensors may be positioned at variouslocations within the treatment system, but are preferably positionednear the ozone entry ports in the ozone delivery system.

Yet another aspect of the invention provides ozone sensors positioned atstrategic positions both inside and outside the storage/treatmentchamber. Ozone sensors positioned inside the chamber may indicate theconcentration of ozone in any particular location in the chamber.Positioning ozone sensors at the exit ports where the gas may beevacuated from the chamber allows for detecting ozone leakage out of thechamber. When ozone leakage is detected, the chamber may be sealed, andthe ozone supply may be suspended until the leakage is controlled.

A further aspect of the invention provides pressure sensors positionedat various locations within the ozone treatment system. When thepressure inside the chamber reaches a certain level, the pressuresensors may cause the gas vents in the treatment chamber to open.

The treatment system may also comprise ozone destruction units,preferably positioned at the exit ports of each vent or at the end of amanifold coupled to the exit ports. When the exit vents are opened, itis preferred that the ozone gas passes through ozone destruction unitsplaced down stream of the vents so that the ozone is destroyed before itis released into the atmosphere. Ozone destruction units provided by theinvention preferably decompose any ozone passing through them tomolecular oxygen. A particular ozone destruction unit may be activatedwhen the ozone vent or vents connected to it are opened, thus preventinguncontrolled release of ozone gas into the atmosphere.

During the treatment process, it may be desirable to remove samples ofthe treated products to assess the progress of the decontamination. Theinvention provides sampling devices that may be incorporated into thetreatment system. The sampling capabilities provided by the inventionallow safe withdrawal of one or several samples from different depthswithin the chamber so that representative samples may be analyzed.

The invention provides an apparatus comprising a manifold for ozonedelivery to a matrix of contaminated product or product to be preserved.The manifold may be connected to a treatment/storage chamber through amultiplicity of entry ports. Preferably, each entry port may becontrollably closed or opened as needed to supply ozone or ozonecontaining gas to particular locations within the treatment chamber. Thetreatment chamber may also comprise a plurality of ozone exit ports.Each exit port may be placed in a location that would allow theevacuation of ozone gas that enters the chamber, primarily from acorresponding ozone entry port. The coupling of ozone entry and exitports may provide better control of ozone flow through any particularportion of the chamber. For example, an ozone entry port and acorresponding exit port may be opened simultaneously so that ozone flowmay be directed to a particular portion of the treatment chamber. As thetemperature and/or ozone concentration increase within the portionsubjected to ozone flow, the ozone entry and exit ports may be closedand a different set of ozone entry and exit ports may be opened todirect the ozone flow to a different portion of the treatment chamber.

The invention also provides for parallel treatment of more than oneportion of product in the treatment chamber. It is preferred howeverthat portions of the product being treated at the same time be somewhatseparated by one or more portions with entry and exit ports beingclosed. Isolating the portions being treated may provide better controlof the changes in the temperature and ozone concentration.

Coupled ozone entry and exit ports may be distributed throughout theozone delivery manifold and the treatment chamber so that the totalozone flow within a given treatment run may cover all areas within thetreatment chamber. Furthermore, ozone sensors and temperature sensorsmay be coupled to each set of ozone entry and exit ports. When thetemperature indicated by a particular sensor rises above a given valueand/or the ozone concentration measured by the corresponding ozonesensor increases above another given value, a signal may be sent, forexample to a relay that would close the ozone entry and exit portsassociated with the portion of the treatment chamber where overheatingand/or ozone overflow may have been detected and open another set ofozone entry and exit ports.

Intermittent supply of ozone to different sections of the treatmentchamber may permit continuous use of ozone without turning the entiresystem off due to overheating or over exposure to ozone in any one ormore portions of the treatment chamber. A shut down of the supply ofozone to the entire treatment chamber may be necessary only when ozoneand/or temperature sensors indicate high ozone levels and/or hightemperatures in all the sections of the treatment chamber.

In one aspect of the invention, contaminated product may be introducedfrom a hopper into the treatment chamber, such as by a particle conveyorof the auger type, where the product may be exposed to humidified and/orpreheated sterilizing gas, such as ozone or ozone containing gas. Thetreatment chamber may be maintained at a pressure slightly belowatmospheric to contain the gas inside the treatment chamber. Internalpressure may be monitored by a pressure sensing device which may send asignal to a valve controller to open a valve to a vacuum when thepressure in the chamber reaches a given value. The vacuum valve openingmay permit gas discharge and maintain the chamber under a desiredpressure.

Another aspect of the invention provides an apparatus that may operatein a cyclic treatment regime. The regime may comprise a filling phaseand a contacting phase. In the filling phase, ozone may be introducedevenly throughout the contaminated product, for example by usingmultiple gas distribution ports. Monitoring and feedback controlmechanisms may be included in the system for better control of the rateof ozone dosing. The conduit connecting the treatment chamber containingthe contaminated product to the ozone delivery system may initially bepartially open so that the chamber may be provided with ozone.

Ozone and temperature monitoring devices may be used to control theamount and rate of ozone bearing gas being introduced during the fillingphase. When ozone content and/or the temperature in the treatmentchamber reach a given value, the conduit connecting the treatmentchamber to the ozone delivery system may be closed and the chambersealed until the ozone content and the treatment chamber temperaturedrop below another given value. Controlling the concentration and/orquantity of the ozone delivered to the chamber may prevent local heatingand provide an even distribution of the ozone bearing gas through thetreatment chamber. Controlled ozone delivery may be used to build up theozone concentration in spaces between the materials up to a desiredlevel.

Once the desired ozone concentration is reached, the treatment chambercontaining the stored material may be sealed or blocked in, and ozonedelivery may be stopped. After the suspension of the ozone supply,contact and reaction between the ozone in the chamber and thecontaminated material proceeds until all of the ozone is consumed. Thecontacting phase is determined by the time necessary for the consumptionof all the ozone supplied to the treatment chamber during any fillingphase. At the end of a contacting phase, another filling phase may beinitiated and the filling-contacting cycle may be repeated as many timesas desired until the contaminants in the product drop to an acceptablelevel, at which time the treated product may be withdrawn and thetreatment or storage chamber recharged with another batch ofcontaminated product.

In yet another aspect of the invention, ozone may be generated on-siteand forced, under pressure, into one of several containers where thematerial to be treated may be held. A controlled valve system,comprising one or more valves, may direct the ozone into one or morecontainers. When an adequate quantity of ozone has been supplied to, andcirculated through the container or containers, the ozone gas flow maybe cut off and diverted, using the valve system, to the next containeror set of containers. While the second set of containers is beingfilled, the ozone in the first set of containers may be reacting withthe material which may be detoxified. As the second set of containersbecomes full or otherwise contains an adequate amount of ozone, theozone supply to the second set of containers may be stopped, the secondset of containers sealed and ozone delivery to the first set ofcontainers resumed and/or ozone delivery to a third set of containersinitiated. Intermittent ozone flow in different sets of containersallows efficient use of the ozone, which may be continually generatedon-site and delivered to the containers until all of the product in thestorage units has been treated.

In a further aspect of the invention, contaminated product, and orproduct to be preserved from contamination, may be moved around insidethe treatment chamber continuously or intermittently during the exposureto ozone. Ozone or an ozone containing gas may be delivered down achannel, of a hollow auger for example, with holes machined on itssides. The channel is preferably placed at the center of the treatmentchamber. The ozone may flow through the holes in the channel and intothe spaces around the product. Optionally, the auger may be rotated, forexample by a motor, preferably a variable speed motor.

Optionally, the ozone delivery system may comprise wings placed alongthe side of the auger, preferably adjacent to each hole, allowing foreven better distribution of the ozone through the matrix by lifting theproduct upwards through the storage treatment chamber as the auger isrotated. When the temperature and/or pressure inside the treatmentchamber reach a given value, a signal may be sent to cut off the supplyof gas to the chamber. The ozone concentration within the chamber may becontrolled and adequate ozone concentration inside the treatment chambermay be maintained by either resuming the supply of ozone when low ozoneconcentrations are detected, or stopping ozone delivery and forcing theozone through exit ports, preferably through ozone destruction unitsplaced down stream of the ozone exit ports, when high ozoneconcentrations are detected.

In another aspect of the invention, a gas circulation system, such as acirculating loop placed around the storage/treatment unit, may be addedto the treatment system. The ozone may first be directed from one ormore of the ozone exit ports into the circulation system, and thendirected into the treatment chamber unit.

FIG. 1 is a schematic diagram of an ozone delivery and treatment system10 of the present invention. The treatment system 10 may be useful indecontaminating all types of agricultural products, and the system isparticularly useful in decontaminating agricultural or particulate foodproducts, such as whole grain, seeds, fruits, grasses, and nutscontaminated with mycotoxins. The system is also useful in preventingcontamination during the storage of these products. The system 10comprises a chamber 12 suitable for treating and optionally storingagricultural products. The chamber may be made of any rigid materialcapable of supporting the weight of the product, although an ozoneresistant material or material having an ozone resistant coating ispreferred so that the system may be operated for long periods of time.It is also preferable that the chamber be suitable for filling withagricultural products such as whole grain, seeds, fruits, grasses, andnuts by conventional methods such as an auger, a conveyor, pneumaticflow, etc. The treatment system 10 comprises an ozone generating unit 14optionally connected to a humidifier 18 for optionally humidifying theozone before it is supplied to the treatment chamber. The ozonegenerating unit and the humidifier are provided in fluid communicationby a conduit. A pump 16 is optionally placed between the humidifier andthe ozone distribution system 22 which delivers the ozone to thetreatment chamber at various gas entry ports 24. In accordance with oneaspect of the invention, each entry port 24 is matched with acorresponding ozone exit port 26 to provide enhanced control of the flowof ozone in selected locations of the product matrix 28 within thechamber 12. While any number of entry and exit ports may be utilized, anexemplary ozone distribution system 22 comprises six ports of ozonedelivery to the treatment chamber. All entry ports are also coupled toan inlet manifold 32 which is supplied with ozone that is pumped throughthe humidifier by the pump 17. All ozone exit ports 26 are coupled to orin communication with an outlet manifold 34 which is in turn incommunication with an ozone destruction unit 36 in which any remainingozone is destroyed so that no ozone is released into the atmosphere.

The treatment system optionally further comprises a gas source 38 formixing with ozone before delivery to the treatment chamber. The gassource 38 allows independent control of the pressure or ozoneconcentration inside the treatment chamber without changing the flowrate or quantity of ozone supplied to the product matrix. The gas source38 is preferably a nonreactive gas, such as an inert gas, but maycomprise other treatment gases.

The pressure inside the chamber is preferably detected and monitored bypositioning pressure sensors 42 at various locations inside the chamber.The temperature is preferably detected and monitored by a set ofthermocouples 44 distributed throughout the chamber 12, most preferablyadjacent the ozone entry ports 24, so that local overheating may bedetected as early as possible. The ozone concentration in the chamber 12is preferably detected and monitored by a plurality of ozone sensors 46positioned at various locations within the chamber 12, most preferablyadjacent the ozone exit ports 26. The ozone sensors allow earlydetection of ozone flow in the relevant region or zone of the chamber.For example, ozone flow in overexposed sections of the matrix may bestopped by closing the ozone entry and exit ports that supply ozone flowto the sections where over-exposure to ozone has been detected.

Finally, the treatment system 10 may optionally further comprise a gascirculation system 48 that is operated to provide a gas flow through theproduct matrix when needed. The gas circulating system 48 may beoperated to redistribute ozone inside the treatment chamber or toevacuate remaining ozone when the treatment is completed or suspended.

FIG. 2 is a schematic diagram of an ozone delivery system 50 that can beused in conjunction with the ozone treatment system of FIG. 1. The ozonedistribution system 22 may be optionally replaced by or used inconjunction with the alternative ozone delivery system 50. The ozonedelivery system 50 comprises an ozone resistant hollow tube 52 withholes 54 perforated along at least a portion of its length. The ozonedelivery system 50 may be placed down the center of the chamber 12 andextend a major portion of the distance from the top of the chamber tothe bottom of the chamber. Ozone may be supplied through the holes 54 tovarious sections within the treatment chamber. The ozone delivery system50 may be used in replacement of or in conjunction with the ozonedistribution system 22. When the ozone delivery system 50 is used inconjunction with the ozone distribution system 22, ozone may be suppliedfrom the ozone generator unit 14 or humidifier 18 to the treatmentchamber through both the inlet manifold 32 and the hollow tube 52. Theozone delivery system 50 is optionally coupled to an agriculturalproduct loading system (not shown.) The agricultural product may beloaded into the chamber 12 a conventional agricultural apparatus, suchas an auger, a conveyor, a conveyer belt, a bucket, etc. In thisconfiguration, the product may be loaded through port (not shown)located at or near the top of the chamber 12. A sensor (not shown)allows monitoring and control of the filling of the chamber 12 with theproduct. Strategically positioning the loading system (not shown) at thetop of the treatment chamber allows the agricultural product to surroundthe ozone delivery system 50 as it is loaded, forming the matrix 28around the ozone delivery system 50.

FIG. 3 is a schematic diagram of a multiple-chamber ozone treatmentsystem 60 of the present invention. The multiple-chamber system 60comprises a plurality of chambers 62 communicating with at least onecommon ozone source 64. Each chamber 62 is in communication with theozone source 64 through a dedicated conduit 66 and an ozone deliverysystem comprising a hollow tube 65 extending along the center of thechamber and branches 69 perpendicularly extending from and incommunication with the hollow tube 65. Ozone flow into the conduits 66and the hollow tube 65 is optionally controlled by a valve system 68which allows for selective supply of ozone to one or more of thechambers 62 at any given time. The multi-chamber treatment system 60allows more efficient use of the ozone because the ozone may beselectively supplied to one or more chambers allowing continuous use ofthe generated ozone even when ozone supply to one or more chambers issuspended. The system 60 is also more efficient because it allows theuse of smaller ozone generating systems in the treatment of largequantities of contaminated product. Furthermore, the system 60 allowsone or more chambers to be filled with ozone while the ozone in one ormore other chambers is contacting the product.

FIG. 4 is a schematic diagram of an ozone treatment system 70 with arotating ozone delivery mechanism 72 similar to the ozone deliverysystem 50 of FIG. 2. The system 70 also comprises an ozone generator 71in communication with the ozone delivery mechanism 72. A humidifier 73and one or more pumps 75 may optionally be positioned in the passagecommunicating the ozone generator 71 with the ozone delivery mechanism72. The system 70 also comprises an ozone monitor 77, an ozonedestruction unit 79, a pressure sensor 83, and a temperature sensor 85.A motor 74 is coupled to the ozone delivery system 50 in order toperiodically or continuously rotate the delivery mechanism 72 to allowfor better distribution and circulation of the ozone throughout theproduct matrix 28 by delivering the ozone in different directions in theproduct matrix 28 as the ozone delivery system is rotated. The motor maybe operated at various speeds and the direction of rotation may bereversed as desired.

FIG. 5 is a schematic diagram of an ozone delivery system 82 with arotating mechanism and a set of wings. The ozone delivery system 82 issimilar to the ozone delivery system 72 of FIG. 4 with the addition ofwings 84 encircling the tube 88 adjacent or between the holes 86. Thewings 84 are extended in an angled direction from the tube 88 and faceupwards towards the top of the chamber 12 to lift the product upwardsthrough the chamber as the ozone delivery system 82 is rotated. Thelifting of the product in the immediate vicinity of the ozone deliverysystem allows better mixing of the product matrix by continuouslyreplacing the product immediately exposed to the ozone, resulting in amore uniform treatment of the contaminated product. Optionally, themixing of the product may be improved by using wings with an wavy shapeallowing even easier lifting of the product.

FIG. 6 is a schematic diagram of an ozone treatment system 90 similar tothe ozone treatment system 10 of FIG. 1 with the ozone delivery system22 replaced with an ozone blower 92. The ozone blower 92 provides analternate mechanism for delivering the ozone uniformly to the productmatrix 28. The ozone blower 92 is in communication with the ozone source94. A humidifier 96 may optionally be positioned in the passage betweenthe ozone source 94 and the ozone blower 92. The ozone blower 92 may beused separately or in conjunction with the air blower 48 of FIG. 1. Theozone blower 92 may optionally be substituted with or coupled to a gascompressor. Also, the ozone delivery mechanisms 22, 50 and 92 may beused separately or together within one single treatment system such asthe system 10 depicted in FIG. 1.

The following examples show the function of the present invention andsome of its preferred embodiments.

EXAMPLE 1

This example illustrates the treatment of mycotoxin contaminated cornwith a continual flow of ozone.

The data presented in Table 1 illustrate the efficacy of the inventionin detoxifying mycotoxin contaminated whole corn. One (1) kg ofaflatoxin contaminated whole kernel yellow corn was placed in atreatment chamber. Ozone gas was generated electrochemically to obtain agas stream with an ozone concentration of about 10 wt % in oxygen. Theozone was humidified by mixing with water by passing the gas through acolumn of water to obtain a gas stream with over 80% humidity. A seriesof ozone resistant tubes connected the ozone generator to the treatmentchamber, and a series of valves in the tubes were used to control theflow of ozone into the chamber. A pressure sensor was disposed in thechamber in order to open an outlet valve when pressure build-up withinthe treatment chamber was detected. The outlet connected to an ozonemonitor to detect ozone gas exiting the treatment chamber. Theelectrochemical generation of ozone allowed the supply of an ozonestream capable of penetrating the product matrix and overcoming anyresistance that may be exerted by gases already present in the chamber.Temperature probes were also placed inside the treatment chamber tomonitor temperature changes. Ozone was passed through the chamber for 96continuous hours. Samples were removed for analysis at different timesduring the treatment. The decrease in the aflatoxin contamination as afunction of the amount of ozone provided to the contaminated product isreported in Table 1.

FIG. 7 is a graph illustrating the decrease in aflatoxin concentrationin one (1) kg of contaminated corn as a function of exposure time to acontinuous stream of ozone gas. The graph shows that after 1 hour oftreatment, the corn was decontaminated to the point where it couldconstitute acceptable feed to finishing cattle. Further treatment, up to4 hours, reduced the aflatoxin contaminant to a level where it could besafely fed to breeding cattle and mature poultry. As shown in the graph,treatment for only 16 hours drastically decreased the concentration ofaflatoxins yielding decontaminated corn that could be safely fed todairy cattle without the risk of contaminating the milk. However,exposure to ozone for more than 16 hours was necessary for the reductionof aflatoxins in the corn to levels undetectable by HPLC.

This example presents the data obtained in a second continuous ozoneflow experiment. The experimental set-up used in this example wasidentical to the one operated in Example 1, except that the treatmentchamber was pressurized to 20 psi. A backpressure valve was positionedin the chamber near the exit port. A positive pressure build up insidethe chamber is created and sustained by the supply of the ozone throughthe self compressing electrolysis process. The data reported in Table 2illustrate the decrease in aflatoxin concentration as a function of thetime of exposure to ozone and the amount of ozone used. The data showthat the decrease in mycotoxin concentration as function of the durationof the exposure to ozone, generally followed the same profile indicatedby the results obtained in Example 1.

TABLE 1 Data obtained from an experiment where ozone gas (178 mg/min.)was passed through 1 kg of aflatoxin contaminated corn in a continualflow ozonation treatment. Aflatoxin Ozone Dose Concentration (grams) 0hour mean 1220.2 ppb 0 1 Hour 228.0 ppb 242.0 ppb 10.68 Mean 235.0 ppb 4Hours 59.8 ppb 64.2 ppb 42.72 Mean 62.00 ppb 16 Hours 13.8 ppb 10.8 ppb170.88 Mean 12.30 ppb 96 Hours 0.0 ppb 0.0 ppb 1025.28 Mean 0.00 ppb

TABLE 2 Data obtained from an experiment where ozone gas (178 mg/min.)was passed through 1 kg of aflatoxin contaminated corn in a continualflow ozonation treatment and a pressure of 20 psi. Aflatoxin Ozone DoseConcentration (grams) 0 hour mean 1220.2 ppb 0 1 Hour 289.2 ppb 295.6ppb 10.68 Mean 292.4 ppb 4 Hours 328.7 ppb 104.6 ppb 42.72 Mean 216.65ppb 16 Hours 82.2 ppb 95.0 ppb 170.88 Mean 88.6 ppb 96 Hours 0.0 ppb 0.0ppb 1025.28 Mean 0.00 ppb

EXAMPLE 3

This example illustrates intermittent ozone flow treatment using thecyclic treatment capabilities of the two phase system of the invention.Unlike Examples 1 and 2 where the ozone gas was continuously passedthrough the treatment chamber, the experiments reported in this exampleused a treatment cycle comprising a succession of “filling” and“contacting” phases. A set of electronic timers were used to switchbetween the phases.

The first step was determining the initial amount of ozone needed totreat the contaminated corn disposed in the treatment chamber. Theozone/oxygen gas was generated by an electrochemical cell and humidifiedby adding water by passing the gas through a water column. A valvelinking the ozone generator to the treatment chamber was opened andozone gas flowed into the chamber through a vertical, centrallydisposed, hollow tube with a plurality of holes in the side. An ozonemonitors was placed at exit ports within the treatment chamber to detectozone exiting the treatment chamber. When the concentration of ozone gasexiting the chamber reached the concentration in the gas entering thechamber, valves connected to the entry and exit ports were closed,sealing the treatment chamber, and signaling the completion of thefilling phase of the treatment cycle. The temperature was continuouslymonitored through thermal probes and ambient pressure was maintainedinside the chamber. The design used in this example included a mechanismfor pumping an inert gas through the system to displace the ozone.During the second phase of the treatment, the ozone was allowed tocontact and react with the corn without providing any additional ozonegas to the chamber until the ozone concentration dropped to zero, atwhich point a sample of the corn was analyzed and another cycle offilling and contacting was initiated if needed. Analysis of the datarevealed that one (1) hour was a sufficient period of time for all theozone in the chamber to react with the mycotoxins or otherwise degrade.Thus the contacting phase was allowed to proceed for 1 hour in eachcycle. At the end of each contacting phase, a sample of the corn wasremoved and analyzed for determining mycotoxin concentration.

FIGS. 8(a-b) are graphs illustrating the amount of ozone supplied to thetreatment chamber during the first and fourth filling phases,respectively, in a series of successive treatment cycles. The graphsshow the variation in the UV absorbance at 255.3 nm as a function ofozone filling time in minutes. Ozone was supplied to the chamber untilthe absorbance of the exiting gas reached a maximum. FIG. 8(a) showsthat for the first cycle, the chamber was supplied with ozone gas for 10minutes before the concentration of the exiting ozone reached a plateausignaling the end of the filling phase. At the end of the filling phase,the chamber was sealed and the ozone already in the chamber was allowedto contact the product without additional supply of ozone. FIG. 8(b)shows the ozone filling profile of the filling phase in a fourth cycleinitiated after the ozone supplied to the chamber during a third cyclewas totally consumed. The graph shows that the time required to fill upthe chamber with ozone to a point where the concentration of exitingozone reaches a plateau in the fourth cycle was much shorter than thetime required in the first cycle, in the fourth cycle, three (3) minutesof ozone supply were sufficient for the concentration of exiting ozoneto reach a plateau while 10 minutes were necessary to fill up thechamber with ozone during the first cycle.

Table 3 shows how the aflatoxin concentration dropped as the number oftreatment cycles increased. The data show that the “two phase” treatmentcycle was effective in removing the aflatoxin present on the corn.

TABLE 3 Data obtained from an experiment where ozone gas (178 mg/min.)was passed through 1 kg of aflatoxin contaminated corn in anintermittent flow ozonation treatment with the reactor being filled withozone for 10 min every hour. Aflatoxin Ozone Dose Concentration (grams)0 Treatment Cycles 1220.2 ppb 0 Standard Deviation 146.6 ppb 4 TreatmentCycles 274.8 ppb 256.4 ppb Mean 265.6 ppb 7.12 Standard Deviation 13.01ppb 16 Treatment Cycles 170 ppb 130 ppb Mean 150 ppb 14.24 StandardDeviation 20 ppb 24 Treatment Cycles 57.0 ppb 59.0 ppb Mean 58.0 ppb28.48 Standard Deviation 1.41 ppb 32 Treatment Cycles 35.0 ppb 42. ppbMean 38.5 ppb 42.72 4.95 ppb 48 Treatment Cycles 8.2 ppb 7.8 ppb Mean8.00 ppb 57.0

EXAMPLE 4

This example discusses the results of a turkey feeding study in whichone day-old female turkey poults were exposed to aflatoxin contaminated,ozonated and control corn diets. A toxicological feeding study usinganimals that are sensitive to the toxicity of aflatoxins was conductedin order to demonstrate actual detoxification of aflatoxins using ozone.One objective of this animal study was to evaluate the capability ofelectrochemically-produced ozone gas to degrade AfB₁ innaturally-contaminated whole kernel corn and confirm detoxification inturkey poults.

Corn was procured from the southern coastal area of Texas and analysisby high performance liquid chromatography (HPLC) revealed 1,220±73.3parts per billion AfB₁. The corn was treated in a reactor with a 35 kgcapacity for whole kernel corn. The reactor was set up according to thedesign described in FIG. 3. The ozone generator was connected to thetreatment chamber with a series of valves and ozone resistant tubing.Ozone gas was evenly distributed throughout the system using a number ofhollow tubes with holes drilled along the length of the tubes. Thestructure was branched to provide the best ozone distribution throughthe corn. Control and contaminated corn were treated for 92 h with O₃ at200 mg/min in 30 kg batches; decontamination of the corn by reduction ofmore than 95% of AfB₁ in the contaminated corn was achieved.

The ground corn was mixed with a commercial soybean meal (SBM) basedconcentrate (46:54 by weight, respectively) that contained or exceededlevels of nutrients recommended by the National Research Council (1994).By blending the corn with SBM, the concentration of AfB₁ was effectivelyreduced by 54%. The SBM ration was free of any detectable mycotoxins andcontained no antibiotics, coccidiostats or growth promoters. A dietcontaining corn that had no detectable aflatoxin was formulated in asimilar fashion.

Day-old female British UTA turkey poults were individually weighed,wing-banded and randomly distributed into four equal sets. Six replicateof five poults per pen (n=30 per treatment) were grouped based on thefollowing dietary treatments: 1) control feed containing uncontaminatedcorn, 2) control feed containing uncontaminated corn treated with 10 wt% O₃ at 200 mg/min for 92 h, 3) feed containing corn contaminated withAfB₁ and 4) feed containing corn contaminated with AfB₁ treated with 10wt % O₃ at 200 mg/min for 92 h. Turkeys were housed in electricallyheated batteries under continuous fluorescent illumination with forcedventilation and provided feed and water ad libitum.

Poults were individually weighed and feed consumption for each replicatewas recorded weekly. At 3 weeks of age, 18 poults (6 replicates of 3poults each) from each treatment group were bled by cardiac puncture forserum biochemical analyses and 12 samples from the same poults (6replicates of 2 poults each) from each group were used for hematologicaldeterminations. Four groups of 18 poults were killed by cervicaldislocation and the liver, kidney, spleen, pancreas, proventriculus,bursa of Fabricius and heart were dissected and weighed.

When compared to controls, relative weights of the kidney, spleen,pancreas, proventriculus and bursa of Fabricius increased in poults fedthe aflatoxin corn diet, whereas the mean relative weight of the liverdecreased and the liver appeared greatly discolored. There was a totalprotective effect by treating the aflatoxin corn with ozone for theliver, kidney, spleen, pancreas, and proventriculus and a partialprotection for the bursa of Fabricius. The discoloration of the liverdue to the contaminated corn was eliminated by O₃ treatment.Additionally, relative organ weights and liver color were not affectedby treatment of control corn with ozone.

The corn contaminated with aflatoxin caused significant changes in serumenzyme activities and hematological values. Significant increases wererecorded for creatinine kinase, aspartate aminotransferase, alanineaminotransferase and lactate dehydrogenase in poults receiving theaflatoxin corn diet. These effects were completely mitigated bytreatment of the aflatoxin corn with ozone. Erythrocyte counts, meancorpuscular hemoglobin and mean corpuscular volume were increased in theaflatoxin corn group. However, birds consuming the diet containing theaflatoxin corn treated with ozone did not differ from controls in thesehematological parameters. In addition, serum enzyme activities andhematological values for poults fed the ration containing control corntreated with ozone were not different than activities and values forcontrols. The aflatoxin corn caused a significant decrease in serumconcentrations of triglycerides, cholesterol, calcium, total protein andalbumin. Ozonation of the aflatoxin corn alleviated these changes;poults on diets containing ozone-treated aflatoxin corn had values thatwere not different than controls. No poults fed control corn treatedwith ozone had any serum chemical values different than controls.

These data demonstrate that treatment of contaminated corn withelectro-chemically produced O₃ provided protection against AfB₁ in youngturkey poults. It is important to note that treatment of control cornwith O₃ did not alter the growth performance, organ weights, orblood/serum chemical and biochemical values of the turkey poults.

EXAMPLE 5

A series of laboratory comparisons were made by treating a batch ofaflatoxin contaminated yellow dent whole corn and a batch of aflatoxincontaminated ground yellow dent corn under identical conditions. Theexperimental data is shown in Table 5. The table shows considerabledecrease in aflatoxin concentration on the whole grain corn while theground corn shows very little change in the aflatoxin concentration. Thecost of ozone treatment is dependent on the “ozone demand” of the matrixsupporting the aflatoxin species. In the case of the whole corn kernels,the ozone demand is low and therefore the amount of ozone wasted inreactions other than the oxidation of aflatoxin (corn carbohydrates,oils, proteins) is minimal. In treating ground corn, the ozone demandwas almost 20 times the quantity of ozone required by the treatment ofwhole corn. Another consequence of the high ozone demand in thetreatment of ground corn is a sharp rise in temperature that wasobserved during the treatment. With low ozone requirements, thetreatment of whole corn resulted in only a moderate increase in thetemperature, which did not exceed 35° C., while the temperaturesexceeded 80° C. during the treatment of ground corn.

TABLE 4 Data obtained from treating whole corn and corn meal. Percentageof Percentage of Ozone dose Aflatoxin removed % Aflatoxin removed % gO₃/kg corn whole corn ground corn 0 0 0 7.1 78.2 0 28.5 95.2 1.6 67.699.3 4.1

A significant feature of the efficient invention is the use of ozonegenerated by a new electrochemical processes and apparatus. In thismethod, ozone is generated electrolytically from water as opposed to theconventional process in which ozone is generated from molecular oxygenby corona discharge. The advantage offered by the electrochemicalprocess is its ability to generate concentrated ozone (up to 20 wt %)compared to only 2 wt % for an air-fed corona unit or 6 wt % for anoxygen-fed corona unit. The high ozone concentrations allow moreefficient oxidative degradation of toxins. In addition, for small scalesystems, the equipment costs for electrochemical ozonizers are lowerthan for corona discharge units. It should be noted however, that insome aspects of the invention, using conventional ozonizers may provideefficient treatment systems, and such systems are within the scope ofthe present invention.

While the foregoing is directed to the preferred embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims which follow.

What is claimed is:
 1. A method for treating an agricultural productwith ozone comprising the steps of: introducing a stream of humidozone-containing gas into a chamber containing the agricultural product;monitoring the humidity of the ozone-containing gas within at least oneportion of the chamber containing the agricultural product; andadjusting the humidity of the humid ozone-containing gas stream beforethe gas stream enters the chamber to maintain the humidity of theozone-containg gas in the chamber within a desired range.
 2. The methodof claim 1, wherein the humidity of the ozone-containing gas stream inthe chamber is controlled at greater than about 80% humidity.
 3. Amethod for treating an agricultural product with ozone comprising thesteps of: introducing a humid ozone-containing gas stream into a chambercontaining the agricultural product; and contacting the agriculturalproduct with the humid ozone-containing gas stream.
 4. The method ofclaim 3, wherein the agricultural product is selected from feeds forlivestock and food for human consumption.
 5. The method of claim 3,wherein the agricultural product is selected from grains, nuts, fruits,vegetables, alfalfa, clover, sorghum, fescue grass forages, andcombinations thereof.
 6. The method of claim 3, further comprising thestep of maintaining the humidity of the ozone-containing gas within thechamber at greater than about 80% relative humidity.
 7. The method ofclaim 3, further comprising the step of: reacting the ozone with toxins,toxic metabolites, or microorganisms present on the agriculturalproduct.
 8. The method of claim 3, further comprising the step ofintroducing an inert gas into the chamber along with theozone-containing gas.
 9. The method of claim 8, wherein the inert gas ishumidified.
 10. The method of claim 8, wherein the inert gas is carbondioxide, nitrogen, argon, or mixtures thereof.
 11. The method of claim8, further comprising the step of reacting the ozone with toxins presentin the inert stabilizing gas.
 12. The method of claim 3, furthercomprising providing air into the chamber.
 13. The method of claim 3,further comprising the step of scavenging microorganisms in the air. 14.The method of claim 3, further comprising the step of generating theozone-containing gas by a process selected from an electrochemicalprocess, a corona discharge process, and combination thereof.
 15. Themethod of claim 3, further comprising the step of scavengingmicroorganisms in the agricultural product and oxidizing toxins on theagricultural product.
 16. The method of claim 3, wherein theagricultural product is selected from feed for livestock and food forhuman consumption.
 17. The method of claim 3, further comprising thestep of generating the humid ozone-containing gas stream in anelectrochemical cell.